Often, fasteners used to assemble performance critical components are tightened to a specified torque level to introduce a “pretension” in the fastener. As torque is applied to the head of the fastener, beyond a certain level of torque the fastener begins to stretch. This stretch results in the pretension in the fastener which then holds the components together. A popular method of tightening these fasteners is to use a torque wrench. Accurate and reliable torque wrenches help insure the fasteners are tightened to the proper torque specifications.
Torque wrenches vary from simple mechanical types to sophisticated electronic types. Mechanical type torque wrenches are generally less expensive than electronic ones. There are two common types of mechanical torque wrenches, beam and clicker types. With a beam type torque wrench, a beam bends relative to a non-deflecting beam in response to the torque being applied with the wrench. The amount of deflection of the bending beam relative to the non-deflecting beam indicates the amount of torque applied to the fastener. Clicker type torque wrenches work by preloading a snap mechanism with a spring to release at a specified torque, thereby generating a click noise.
Electronic torque wrenches (ETWs) tend to be more expensive than mechanical torque wrenches, and more accurate as well. When applying torque to a fastener with an electronic torque wrench, the torque readings indicated on the display device of the electronic torque wrench are proportional to the pretension in the fastener due to the applied torque. However, the readings also depend on, among other factors, the under head friction between the head of the fastener and the adjacent surface of the component and the friction between the mating threads. Static friction is greater than dynamic friction. Therefore, when torquing operations are initiated, increased amounts of torque may be required to overcome static friction forces and initiate rotation of the fastener. Therefore, it follows that torque is preferably applied to the fastener in a slow and continuous manner to allow friction forces to stabilize, to help insure accuracy and to help prevent over-torquing.
Existing electronic torque wrenches typically have an electronic interface unit that includes a digital torque display, alarm signals, and operating switches, the unit being rotationally fixed with respect to the wrench body. These electronic interface units of fixed orientation are suited for tightening fasteners whose axes are vertical since the user can view the electronic interface unit. However, often these units are not convenient when the user has to tighten fasteners whose axes cause the wrench to be situated such that the electronic interface unit is not readily visible. Although the sound alarm, if present, can be heard in most cases, it is only one of several indicators that the user can utilize to prepare to stop applying torque at the proper time, so as not to over-torque the fastener. When applying torque, the user may use the numerical display to adjust the speed of rotation of the wrench so that he is prepared to stop as soon as he hears an alarm sound and/or sees a light signal. Without the continuous numerical display feedback available, and using only the alarm signals, the probability of over-torquing may increase. In summary, not only is it difficult to apply torque to a fastener while trying to simultaneously view a display at an odd angle, it may also increase the chances of over or under-torquing the fasteners.
Drawbacks present in prior art electronic torque wrenches may lead to the over or under-torquing of fasteners, which can contribute to reduced performance, and eventual failure, of the fasteners.
The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods.